Crimped yarn production



w. H. CHARCH EI'AL 2,518,753

CRIMPED YARN PRODUCTION Filed July 14, 1949 Aug. 15, 1950 IN V EN TORS' WILL/AM .HALE GHARCH WESTON ANDREW HA RE ATTORNEY FRANK KERR SIGNA IGO BY 4 Q,

Patented Aug. 15, 1950 munio STATES PATENT OFFICE- CRIMPED YARN PRODUCTION William Hale :Charcli, Chadds Ford, Pa., Weston Andrew Hare, Kenmore, N. Y., and Frank Kerr Signaigo, Wilmington, DeL, assignors to E. I.

du Pont de Nemours & Company, Wilmington,

Dcl., a corporation of Delaware Application July 14, 1949, Serial No. 104,614

' *B CIaims.

This invention relate to they production of rayon, and more particularly, itrelates to the production of'regen'erated cellulose fibers, filainents, yarns, and the like, having an inherent and permanent crimp,

U. S. Patent No. 2,249, 745discloses a process for the production of new and unique regenerated cellulose, fibers, filaments and yarns having an inherent and permanent crimp; The process of the above-said patent. comprises extruding viscjose, in the form of f laments, into a setting bath which has a'sufiiciently rapid coagulating action, relative to a'nyregenerating action thereof, to coagulate said filaments completely prior to any substantial regeneration thereof, drawing said filaments fromthe point where they are extruded into the bath, the. velocity of extrusion being at least four times thefvelocity of draw-oil. The coagulated filaments are regenerated, for example, by subjecting the same to the action of an acid regenerating bath and are then purified and dried, the drying preferably taking place with the filaments in a free loose condition;

The resulting filaments are substantially'noncrenulate'd, have a strength of between 0.5 and 1.25 grams per denier, and have permanent crimps lying at random in three dimensions. By the-term permanent crimp is meant that the filaments or yarns may be wet with water, then stretched over-that required. to straighten the filaments and allowed to dry in this stretched condition without destroying'the inherent nature of the filaments to regain their crimp by again wetting the same and permitting them to dry in the absence'of tension.

' Although yarns and filaments produced in accordance with j the process of the above-said patent have found many practical commercial uses, they possess some physical characteristics which can be considerably improved. They have alow tenacity (between 0.5 and 1.25, grams per denier) a high elongation '(of the order of 59% dry elongation and 35% wet elongation), a high spontaneous elongation in water (50% or more), and a high degreeof secondary swelling (of the order of 150%). Thelatter two-characteristics prevented :the satisfactory use of the yarn in flat woven fabrics such'as suitings, overcoat fabrics and the like: ,Also, they-could not be-easily produced in fine deniers,"thusi limiting their use in heavy fabrics, or for use as the pile in carpets and It, is an object of this invention to provide a regenerated-cellulose filament or yarn having aninherent and permanent three dimensional. crimp,

2 r and having a relatively high tenacity, 'a'relativ'cly low elongation, a low spontaneous elongation in water; and a low secondary swelling inwate'r It is another object of this invention to provide'a new and improved process for the production of crimped filaments which is not subject to the'objections, above-stated. It is anothenobject 'of this invention to provide a new and"=im'proved spinning bath for the production of crim'ped filaments and yarns byspin'ning with a high jet= velocity: draw-oil ratio. Other objects of theil'l-tvention will appear hereinafter. r

The above objects may be accomplished, in gen:- eral, by extruding viscose, in the form of file;- ments, into a setting bath comprising an aqueous solution containing a borate dissolved therein in an amount equivalent to at least 5% of borax which bath has a pH value between 3.0 and 9.0, and has a sufficiently rapid coagulating action; relative to any regenerating action thereof, to co? agulate said filaments completely prior to any substantial regeneration thereof, drawing the filaments from the point where they are extruded into the bath, the velocity of extrusion being at least four times the velocity of draw-offlstretching the coagulated; substantially non-regenerated filaments at least 25% over their straight length, (i. e., to of their originally formed length) and regenerating, and drying, the stretched filaments while maintaining them free from tension. By the proceess of this invention a crimped, very White or colorless, lowswelling, low-wet extension yarn is produced.

The invention will be more readily under stood by referring to the following detailed description when taken in connection with the accompanying illustrations, in which:

Figure l is a diagrammatic, side elevational view, with parts shown in section, of an apparatus suitable for use in carrying outthe process of the invention and 1 I Figure 2 is a similar diagrammatic, side ele: vational view of another form of suitable appa ratus. Referringto Figure 1 of the drawings, refer ence numeral"! designates a setting bath tank containing the borate setting bath. The viscose filament-forming composition is forced through candle filter l 2, conduit l4 and spinneret l6 under sufficient pressure that the velocity of extrusion of the filaments from the spinneret orifices is' at least four times the velocity of draw-off by fee'd wheel 22. The filamentous solution buckles and bends as it is forced into the coagulating, substantially non-regenerating setting bath, thus forming highly crimped substantially nonoriented filaments IS. The filaments I8 are brought together and passed about grooved guide rollers I9 and 20, and then about feed Wheels 22 and 24. The yarn comprising the filaments i8 is passed about the feed wheels 22 and 24 with a sufiicient number of turns to avoid slippage. The peripheral speed of feed wheel 24 is enough greater than that of feed wheel 22 to impart the desired amount of stretch to the yarn. From feed wheel 24 the yarn is dropped onto endless belt 26. This endless belt 26 may comprise a preforated metal base member covered with a fabric which will support the yarn. Preferably the belt 26 is moved, slowly to permit the yarn to pile up in tensionless ringlets thereon.

As the belt 26 moves along, it will carry the loose untensioned yarn under regenerating bath shower 28, one or more washing and purifying bath showers 32 and driers 36 and 38. The baths which are showered onto the yarn will pass throughv the belt, and will be caught in drip pans 30 and 34. The regenerated purified and dried yarn will then be wound onto a bobbin 40 or the like.

In Figure 2 of the drawings, reference numeral 42 designates a pump by means of which the filament forming composition, for example, viscose, is forced through candle filter 44, conduit 46 and spinneret 48. The spinneret is positioned-in a relatively deep setting bath tank 50'so as to provide a suitable head of bath liquid above the spinneret. A tube 52, having a length of from 12 to 36 inches, is positioned a short distance from the face of spinneret 48. Bath liquid from tank 50 will flow through the tube 52 to carry the yarn 64 from the spinneret to squeeze rolls 54 and 56. The pump pressure of pump 42 and the head of bath liquid on the tube 52 are so adjusted that the velocity of extrusion of the filament-forming solution is at least four times the velocity of draw-off, the latter being approximately equal to the velocity of the liquid passing through tube 52.

The liquid passing from the open end of tube 52 is caught in receptacle 58, from which it may be returned to tank 50 by means of conduit 60 and pump 62. The yarn 64 is passed about squeeze rolls 54 and 56 in a path approximately a figure S to avoid slippage. passed about grooved guide rolls 68 and which the positioned in a tank 66 containing a stretching bath liquid. From guide roll 10, the yarn is passed through another set of squeeze rolls [2 and 14. Here again, the yarn is passed about and between the squeeze rolls in such a manner as to avoid slippage of the yarn. The squeeze rolls 12 and 14 are driven at a peripheral speed suificiently greater than that of squeeze rolls 54 and 56 to stretch the yarn the desired amount.

From squeeze roll 14, the yarn 64 is passed around grooved guide rolls l8 and 80 which are positioned in tank 16 which contains a regenerating liquid, for example, an aqueous acid or a boiling bath having the same composition as the setting bath. The yarn is then passed onto a windup bobbin 82 or the like. The yarn wound on the bobbin 82 may then be skeined and subjected to purification and drying procedures in a known manner, or the yarn may be cut into staple after stretching and purified as cut stock on a belt or in a suitable container 01' may be out after purification but before drying. The dryin of the yarn should be carried out with the yarn free The yarn is then 4 from tension to permit the free formation of crimps.

The following examples disclose, in specific detail, preferred methods for the practice of the invention, it being understood that the invention is not limited to the specific details set forth. In the examples, parts referred to are parts by weight unless otherwise indicated.

Example I Viscose made from sulfite wood pulp and having a composition of 7 cellulose and 5% sodium hydroxide and. a viscosity of about 52 poises was ripened to a sodium chloride salt index of 4.8, and then extruded at the rate of 20.0 grams per minute, through a spinneret possessing 100 holes, each hole 0.002 inch in diameter, into an aqueous bath containing 30% ammonium sulfate and 10% borax (Na2B4O1.10HzO) with enough sulfuric acid to produce the desired .The bath had a-pH value of 6.0 and was maintained at a temperature of C. The spontaneously .crimped fibers thus formed were drawn through 25 inches of bath travel at the rate of 14 yards per minute, the jet velocity: draw-off ratio being about 7.4. The coagulated, substantially.non-regenerated filaments wet with bath were then air stretched through a 30 inch air travel (between rollers 22 and 24, Figure 1 to 159% ,of their originally spun length (i. e. 59% stretch). The filaments were collected in a tension-free condition on a tray and in this condition were completely regenerated by contact with a regeneratingbathfor 15 minutes. This regenerating bath was prepared from 30% ammonium sulfate, 10% borax and sufiicient sulfuric acid to yield a pH of 4.0 and was used at a temperature of to C. The filaments thus regenerated were very white and substantially free from sufur, the borax bath .thus acting to desulfur as well as to regenerate. The completely regenerated fibers were washed free of salts, then treated with a 0.5% solution of sulfonated tallow, followed by drying in the air at room temperature in a substantially tension-free condition. The resultant fibers possessed the following physical properties: a denier per filament of 9.4, dry tenacity of 1.46 grams per denier, wet tenacity of .74 grams per denier, dry elongation of 34%, wet elongation of 14%. Spontaneous elongation in water was 13% and secondary swelling 99%.

Example II Viscose prepared with 7% cellulose and 5% sodium hydroxide was ripened to a sodium chloride salt index of 4.9, and then spun as in Example I into'an aqueous bath containing 25% ammonium sulfate and 15% borax maintained at a pH of 7.0 and a temperature of 60 C. The crimped filaments formed were drawn through 25 inches of bath travel at the rate of 12 yards per minute, the jet velocity-draw-oif ratio being about 8.0. The coagulated, unregenerated filaments were air stretched through a 30 inch air travel to 183% (i. e. 83% stretch) of their originally spun length. The .fiaments were collected in tension-free condition and further processed *as described in Example I. The resultant filaments possessed a very fine three dimensional crimp and the following physical properties: denierper filament of 8.5, dry tenacity of 1.35 grams per denier, wet tenacity of 0.67 gram per denier, dry elongation of 21%, wet elongation of. 16.4%. Spontaneous elongation in water was 6% and secondary swell ing 91%.

Example III A 7% cellulose 5% sodium hydroxide viscose ripened to a salt index of 4.8 was spun as in Example I into an aqueous bath containing ammonium sulfate, 10% borax and 7.5% sodium sulfate adjusted to a pH of 6.0 by means of sulfuric acid and maintained at a temperature of 58 C. The crimped filaments formed were drawn from the spinning bath at the rate of 12 yards per minute, the jet velocity-draw-off ratio being about 8.1. The coagulated, unregenerated filaments were air stretched through a inch air travel to 150% (i. e. 50% stretch) of their originally spun length. The filaments collected in tension-free condition were further processed as in Example I. The physical properties of the yarn thus obtained follow: denier per filament 14.7, dry tenacity 1.47 grams per denier, wet tenacity 0.67 gram per denier, dry elongation 33.4%, wet elongation 14.9%. Spontaneous elongation in water was 17%.

Example I V Viscose of 7% cellulose, 5% caustic composition was ripened to an index of .7 and was spun into a bath composed of 22% (NHQzSOr, 12% borax, 2.3% Nazsm, 63.8 water at 6.7 pH and 70 C. The viscose was delivered at 50 grams per minute to the spinneret of holes, .0025" 1 hole diameter, and after 66 bath travel the yarn was drawn out of the bath at 41 yards per minute, then stretched to 135% of its initial length. The yarn was collected tension-free and regenerated in a bath of 12.5% (NH4)2SO'4, 7.5% borax, 3.0 pI-I at 100' C. The yarn of good crimp had properties as follows: 21.8 denier per filament, 1.5 g. p. d. dry tenacity, .55 gram per denier wet tenacity, 23% dry elongation and 11% wet extension.

The process of the present invention may be carried out with the use of any viscose filamentforming composition heretofore used in the production of viscose rayon yarns. The viscose may, for example, contain between 5% and 10% cellulose, 3% to 10 caustic soda, and it may have a sodium chloride index of between .5 and 7. Preferably, however, viscose having a cellulose content of between 6% and 8%, a caustic soda content of between 4% and 7% and a sodium chloride index of between. 3.5 and 6.0 is used. The index, however, may be 0.7 or even less, as shown in Example IV. The use of viscose of low salt index, as does the use of low caustic viscose (4% or less) permits the spinning of crimped yarn at maximum spinning speed. The viscose may contain modifying agents, for example, delustering agents, dye adjuvants, heat stabilizing; agents and the like. The cellulose may be modifled by chemical means as by the introduction of ethoxy, hydroxyethyl or carboxymethyl groups provided only that good viscose solutions may be made from the modified ce'llulloses.

The coagulating or setting bath employed in carrying out the present invention must contain, as an essential filamentcoagulating agent, a borate for instance an alkali metal borateor, ammonium borate. In order that the borate will function as an essential filament-coagulating agent, it must be present in such amount thatthe borate content of the bath will be at least equivalent to that of a bath containing 5% borax (NazBcOmlO-HzO). The borate may be added as borax, boric acid or other borate forms as saltsof sodium, potassium, ammonium, amine or the 1 bath as one step in regenerating used baths too like. Other forms may also be'used as, for example, acid borate, hypoborate, metaborate, perborate, tetraborate and pyroborate, as free acids or combined with alkali metal or ammonia.

The coagulating bath must have a pH value of between 3 and 9 so that it will have a sufficiently rapid coagulating action, relative to any regenerating action thereof, to coagulate the filaments extruded therein completely prior to any substantial regeneration thereof. If the pH value is materially less than 3 there will be substantial regeneration before the coagulation is completed, and if the pH value is materially greater than 9.0 the coagulation will be so slow as to present difficulty in preventing filaments from sticking to each other. In general a pH of from 3.0 to 7.0 is preferred. The beneficial effect of the borate ions in the bath is lost if the pH is outside the range of about 3 to about 9.

The coagulating bath can be made up of the proper proportions of boric acid, borax and other neutral salts or borax and acid salts such as ammonium acid sulfate may be used to give the desired pH value. The bath may, however, be made up with the desired quantity of boraX and other neutral salts, and the pH value of the bath adjusted by means of sulfuric acid. In general, any acidic material may be used to get the desired pH, but for economy, sulfuric acid is normally employed.

The coagulating baths of the present invention, containing considerable amounts of alkali metal borates existing as such in the baths having the above-mentioned pH values, are strongly buffered by these borates and considerable quantitles of alkali passing into the baths by the viscose will not change the coagulating action of the bath very fast. This buffering action of the borates permits a uniform coagulation of the viscose over considerable periods of time. Furthermore, the use of borax in the spinning bath greatly reduces spinneret cratering as compared with, prior art coagulating but non-regenerating baths.

Although the coagulating bath of the present invention may consist of an aqueous solution of an alkali metal borate, it should, for best results, also contain other materials commonly used in coagulating baths; for example, ammonium sulfate, glucose, sodium sulfate, sodium bisulfate, sodium sulfrte, and the like. Used alone, the solubilities of the borates are too low for high quali-ty spinning. The addition of other salts enhances the solubility. For example, borax is soluble only to the extent of 11.8% at 41 C. but in the presence of 29% ammonium sulfate and 13% sodium sulfate, solutions containing 25% borax may be prepared at the same temperature. Also ai-nrn-oniumv borate, (NH4)2B4O7.4H2O, and borax enhance each others solubility so that a 23% ammonium borate/15% borax bath may be made up at 41 C. and used for spinnin in this invention and as a regenerating bath at higher temperatures with pH adjusted. In general, it is re ferred to use sulfates with the borates, but other materials, such as those mentioned above or phosphates, thiosulfates, citrates or glycerol may be used instead. For best results, it is preferred to use a sulfate and, for the very best results ammonium sulfate is used.

The presence of a considerable amount of sodium sulfate is desirable from an economic standpointsince then under certain conditions sodium sulfate may be crystallized out of the high in sodium ion. Preferably the coagulating bath is made to contain between 20% and 30% of ammonium sulfate together with between and borax, with the total salt content of the bath being between and 55% with to 45% being preferred. High concentrations may be used. For example, a bath containin ammonium sulfate and 15% borax have been used effectively. Of course, concentrations leading to salt crystallization on guide surfaces, etc. are generally avoided. Concentrations lower than 30% may be used to advantage in spinning baths or in regeneration. For example, very good regeneration was obtained using a bath containing 12.5% ammonium sulfate and 7.5% borax at a pH of 3.0 and a temperature of 100 C. This dilute bath led to desirable shrinkage of yarn spun at high speeds and to enhanced crimp.

A preferred setting bath, for use with a viscose containing 7% cellulose and 5% sodium hydroxide, is one containing 26% ammonium sulfate and 11% borax. Another preferred bath consists of 18% ammonium sulfate, 10% borax and 8% sodium sulfate since by crystallization of a. suitably concentrated bath of this composition, sodium sulfate crystals may be recovered. The setting bath may have any desired temperature if the spinning speeds, spinneret hole, size and spacings, viscose composition, bath travel, etc... are adjusted accordingly. Preferably, however, the setting bath is maintained at a substantially constant temperature within the range C. and 75 C. Since spinning requires but a few seconds, no substantial regeneration occurs at the higher temperature.

The setting baths above-described will have a fast coagulating action with no regenerating action or a slow, delayed regenerating action on the viscose. The yarn is passed through this bath for a distance sufiiciently great to insure its substantially complete coagulation without permitting it to become appreciably regenerated. The exact length of bath travel to accomplish this is, of course, dependent upon such factors as the viscose composition, bath composition, speed of extrusion and draw-off, and bath temperature. Bath travels of the order of 30 inches are generally satisfactory.

As above indicated, the yarns must be spun with a high ratio of jet velocity to draw-off speed. In order that satisfactorily crimped filaments will be formed the jet velocity draw-01f speed ratio should be at least four. This ratio of jet velocity to draw-off speed may, however, be much higher than four, for example, it may be 8, 10, 12, 20 or even higher, depending upon the effects desired in the finished yarn and/or the properties of the viscose and/or setting bath employed.

Immediately after leaving the initial setting bath, the coagulated, substantially non-regenerated yarn, which now possesses a, permanent three-dimensional crimp, is stretched to at least 125% and preferably to at least 150% of its original length. This stretching of the yarn can be carried out in any known manner, for example, in the manner disclosed in the illustrations, above-mentioned. The stretching may be carried out in any desired medium, for example, in the air, in an aqueous salt solution, organic liquid or the like. Preferably the stretching is carried out in the presence of a bath of approximately the same composition as the setting bath.

The stretched yarn is then collected and converted to regenerated cellulose, this conversion preferably being carried out while the yarn is in a 8 relaxed free-to-shrink condition. The regeneration of the yarn, or the completion of the regeneration thereof, can be carried out in any desired manner including treatment of the yarn in an acid liquid, a boiling salt solution, by heat or the like. The regeneration is preferably carried out by immersing the yarns, in a loose condition, for example in skein form, in a. bath similar to the setting bath composition or the stretching bath composition but maintained at a temperature between 80 C. and the boiling point thereof. The yarns are permitted to remain in the regenerating bath until they are completely converted to regenerated cellulose, generally a period of from 10 to minutes. Borate/sulfate baths similar to the setting baths may be used as regenerating baths by employing higher temperatures, as for example, from 75100 C. a

The yarns of this invention are very white in color provided they are regenerated in a borax bath of the type herein defined, with the exception that a lower total salt concentration may be used. The bath is maintained at a pH af about 4 or less. Under these conditions the bath appears to act as an effective desulfuring bath or precipitates the sulfides in a form readily removed. While the mechanism of this action is not known, it has been observed that yarn spun in a non-borax bath of the type described in U. S. Patent 2,249,745 and regenerated in the pH 3.5 borax-ammonium sulfate bath of this invention are considerably whiter than those yarns regenerated in a non-borax bath but still more colored than a yarn spun and regenerated in a borax bath.

Following regeneration, the yarn is purified in the usual manner and dried. The drying step, and preferably also the purification step, is carried out with the yarn substantially free of all tension so that the yarn may be free to shrink and develop the maximum amount of crimp.

In practicing the present invention, it is preferred that the yarn, just prior to drying, be subjected to treatment with lubricating finish, for example, a textile soap, oil, sulfonated oil, mineral oil or other similar textile finish. The finish appears to favorably affect the crimping of the yarn during drying.

The filaments, fibers and yarns produced in accordance with the present invention not only have a very desirable permanent, three dimensional crimp but have many other outstanding physical characteristics. These fibers and yarns, in comparison to yarns produced by the process of Patent No. 2,249,745, possess relatively high tenacities (between 1.25 and 1.60 grams per denier dry, and 0.50 to .85 grams per denier wet), relatively low elongations (between 20% and 40% Wet and. dry), a spontaneous elongation in water not to exceed 35%, and a secondary swelling in Water not to exceed Yarns produced in accordance with the process of U. S. Patent No. 2,249,745, have a dry tenacity of 0.9 to 1.25 grams per denier, a wet tenacity of 0.4 to 0.6 ram per denier, elongations of 35% to 60% wet and dry, a spontaneous elongation in water of 50%, and a secondary swelling in water of The spontaneous elongation in water is determined by measuring the length of a sample of the fiber, followed by immersing it in water at room temperature for sufficient time to permit it to come to equilibrium with the water, and then determining the increase in length of the fiber. (The fiber lengths being measured with the crimps pulled out.) The per cent spontaneous 9 elongation is based on the original length of the dry fiber with the crimp pulled out. The secondary swelling of the fiber is determined by first weighing a sample of the fiber. This is then soaked in room temperature water until equilibrium has been reached. The wet fiber is then centrifuged along with a similarly wet-out fiber with which it is compared in a centrifuge basket having a diameter of 12 inches and a speed of approximately 1500 R. P. M. for 2 minutes. The centrifuged fiber is then reweighed immediately and the per cent secondary swelling'based on the original dry weight of the sample.

The fibers and filaments produced in accordanoe with this invention have a permanent crimp by the definition given above with reference to the filaments produced in accordance with the process of U. S. Patent No. 2,249,745. Whether or not a crimp in a filament or fiber is permanent may also be readily determined by submersing the filamentous structure in liquid ammonia and permitting it to dry without tension. If the crimp is retained in the structure it must be considered permanent.

The exact reasons for the development of these desirable properties in the yarns of this invention are not clearly understood, although they are believed to be directly related to the particular spinning bath employed, which gives a filament as spun of a more dense, les swollen structure andwhich permits greater or more permanent drawing of the gel fibers after coagulation. These baths are similar to those preivously proposed for use in the spinning of permanently crimped regenerated cellulose yarn in that they also exert a rapid coagulating, slow regenerating effect on the extruded viscose solution. Nevertheless, at the same time they differ from those baths in that they possess a buffering action because of the presence therein of the borax or borate ion. This buffering action, as is well understood, permits the bath to possess a relatively constant coagulating action over extensive periods of use, despite the introduction of large amounts of caustic from the extruded solution, and this action together with an evidently specific effect of borate on the extruded viscose solution, apparently accounts for the new and desirable properties of the final yarn.

This invention makes possible the spinning of an inherent, permanently crimped regenerated cellulose yarn that possesses a satisfactory tenacity and a desirable elongation, the yarn extion of fine denier crimped filaments an entirely new field of use for a permanently orimped regenerated cellulose yarn is opened up.

Any departure from the procedure described herein which conforms to the principles of the invention is intended to be included within the scope of the claims below.

We claim:

1. In a process for the production of orimpy filaments by the extrusion of viscose into a coagulating, non-regenerating bath at an extrusion rate of at least 4 times the velocity of drawofi, stretching the resultant filaments and thereafter regenerating said filaments and drying them without tension, the improvement which comprises carrying out the said extrusion in a coagulating, non-regenerating bath containing a borate dissolved therein in amounts at least equivalent to that of a bath containing 5% borax and having a total salt concentration of at least 20%.

2. A process in accordance with claim 1 in which the said borate bath has a pH value of between 3.0 and 9.0.

3. A process in accordance with claim 1 in which the said borate bath has a pH value of,

between 3.0 and 9.0 and the said resultant filaments are stretched to at least 125% of their originally formed length prior to the said regeneration.

4. A process in accordance with claim 1 in which the said borate bath has a pH value of between 3.0 and 9.0 and is heated to a temperature between 45 C. and 75 C.

5. A process in accordance with claim 1 Wherein the said regeneration is carried out in a regenerating bath containing a borate dissolved therein in amounts equivalent to at least 5% borax heated to a temperature of at least 75 C.

6. A process in accordance with claim 1 wherein the said borate bath contains between 5% to 15% borax and 2 to 30% ammonium sulfate.

7. A viscose setting bath which contains between to 15% borax and 20% to 30% ammonium sulfate.

8. A viscose setting bath which contains 5% to 20% borax, to 20% ammonium sulfate and 5% to sodium sulfate.

9. A viscose coagulating, non-regenerating bath which contains 5% to 15% borax and to ammonium sulfate.

WILLIAM HALE CHARCH. WESTON ANDREW HARE. FRANK KERR SIGNAIGO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENT Number Name Date 1,683,199 Lilienfeld Sept. 4, 1928 

1. IN A PROCESS FOR THE PRODUCTION OF CRIMPY FILAMENTS BY THE EXTUSION OF VISCOSE INTO A COAGULATING, NON-REGENERATING BATH AT AN EXTRUSION RATE OF AT LEAST 4 TIMES THE VELOCITY OF DRAWOFF, STRETCHING THE RESULTANT FILAMENTS AND THEREAFTER REGENERATING SAID FILAMENTS AND DRYING THEM WITHOUT TENSION, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT THE SAID EXTRUSION IN A COAGULATING, NON-REGENERATING BATH CONTAINING A BORATE DISSOLVED THEREIN IN AMOUNTS AT LEAST EQUIVALENT TO THAT OF A BATH CONTAINING 5% BORAX AND HAVING A TOTAL SALT CONCENTRATION OF AT LEAST 20%. 